Method of tanning hides.



D SATES PATENT, FFICE.

emcomo nosro AND meme rnaano'rro, or roam, ITALY.

mnrnonor rnnnrme mas.

No Drawing.

To all whom it may concern: 1

Be it known that we, Giacomo Bosro and ANTONIO Pn'nADo'rro, both subjects of the King of Italy, residing-at Turin, in Italy, have invented a certain new and useful Improved Method of Tanning Hides, of whichthe following is a specificatio This invention relates to an improved method of tanning hides by means of tannin or tannic solutions.

In the method hitherto employed of taning hides by means of tannin or solutions containing tannin, the hides after washing, cleansing, etc, are immersed in a succession of vats containing more or less weak tannic solutions.

This method requires considerable labor and time-'the gradations of the tannic liquors of the first bathsbeing always very' low about 9; degree and those of the last baths reach 4 to 5 per cent. Constant manipulation vof the skins is also required in each vat. The hides remain 15 to 20 days in each vat and on removal are submitted to additional tanning in tan-pits or. by means, of rotating drums or other apparatus requiringthe expenditure of mechanical or,

hand. power, and containing more or less strong baths, thus necessitating considerable time .for these different treatments.

( The present invention relates to an accelerated tanning method (based on the employment of'tannin or'tannic solutions) al lowing of obtaining perfectly tanned hidesin a time varying from one day tor thin hides to 15 days for the heaviest hides according to the quality of the hides and their thickness while using for this effect vats onl a v 'l he general idea which 'ded the inventors is that the skininten ed tobe transformed into leatherhas been during the life of the animal at an even temperature varyingwith the nature of the class of animal, for instance approximately 36 '0.

Consequently it is at the life temperature that the tanning operation should be effected in order that the tanning action is produced while theskin retains all the elasticity of the fiber and the natural quantity and density of the gelatin, that is to say,'when is inthe bestcondltion. 2

The method also consists in submitting the to be treated t9" very strong tions of tannin at;.this relatively lug temspecification of Letters Patent.

being produce the adaperature; the gelatino-tannic combination under conditions which 7 Patented May- 14, 1918. Application filed April 19, 1916. SerialNo. 92,1372.

most approach the skin in the vital state and producing a compact and homogeneous leather.

Actin on this principle, the skins (after the was and cleansing process which must be very carefully efiected) are placed in a vat containing concentrated tannic solution heated to the said life temperature of the'respective animals, say, for instance,

34. to 36; it must be stated however that the skins must not'be plunged immediately a into baths of this temperature but the bath must be brought progressively though quickly to the said temperature after the skins are immersed in order to prevent the sudden great diiference of heat between the operations of cleansing and tanning which might harm the skins under treatment. The bath should be heated up to the desired temperature in a relatively very short time, say not more than 2 of an hour.

As in the known methods the skins, could be suspended in the vats on battens or framesfixed or movable, and these vats may either be separate or if desired placed in progressive communication in order to otherwise insure. a relative movement and constant friction of the l quid against the skins; the

important points being that the skins im mersed in the solutions must remain well stretched and without .creases, while however there is constant relative movement with respect to the tannic solution.

In the improved method the skins are thus immersed in ,tannic solution 7 of a strong gradation and heated to the life temperature and maintained at that temperature during practically the whole of the process. This gradation of the liquid can vary (aet to 259 the movement of the liquid relative to them), are immersed-in theco d tannic liquid" above indicated, liquid and skins then being liquid or. are. capable of withstanding Y cording to the product to be'obtained) from B'aum corresponding to 7 to 35% of extract of tan'nin without addition of t manipulated during brought tothe life temperature of the animal which is thereafter maintained during the treatment.

The-baths are prepared by means of dry extract, using any suitable apparatus for such preparation, this extract comprising 60- time the hides'obtained are ready. to receive any kind of finishing work.

Examples.

1. To tan leather intended for sole leather it is necessary to employ during the process a kilogram of extract containing 30130 31%.

of tannin for eachkilogram of hide'aiter the skins have been washed, stripped of hair and flesh, cleaned and finally drained.

This quantity of extract is necessary to fix all the gelatin contained in the fibers oithe sh'n when a firm compact and impermeable leather is to be obtalned.

2. For leathers intended for harness making, Saddlery, etc, or intended to be employed in a more or late soft condition such as for uppers for shoes and boots as the leathers are thencharged with greasy substances, the quantity of tannin employed during the process varies between 600 and 900 grams per kilogram of hide in the dressed condition asin the previous example, according to the thicmess of the leathers and the finish they are to have.

The advantages of the improved method are essentially the following v 1. Economy .07 tiara-The time employed being at the maximum 15 days for very heavy hides is insignificant with regard to that necessitated by the old system which might comprise entire years.

.2. 1Vmp'uZatz'mt.-This is m'l during the operation; the skins do not require tobe the whole time that the tannin treatment lasts.

3. Economy of motive powcr.The use of the fuller being sup ressed the manipulation of which necessitates constant work, there is only the heating of the bath to be efi'ected, which can be obtained very economically Without manipulation solely by the exhaust from steam heaters.- 4. Output.By the favorable conditions obtained by the combination of the heat md of the gelatino-tannic reactions by the meet concentrated tannic liquor, an output of 60 to 62% calculated on the weight of the skins is obtained instead of 50% obtained with the old tanning method.

5. Quality of prcduct. h inally the obtained by this process oil tanning have to lfidays, without removing the essence not their fibers deteriorated, their elasticity remains perfect and their strength is much greater as the following comparative dynamo-metrical tests made on hides treated by the hmown processes and by the present process show.- The resistances to rupture per square sectional millimeter are- For leathers for machine belting treated by the old process 3 kg: 300 1 For the same leathers treated by the present process"; 3 kg. 4200 For sole leathers treated by the old processes 2 kg. 300 For similar leathers treated by I the present process. 2 kg- 860 lf itis desired to give the leathers treated by the present method the appearance ob' tained by the old tanning methods'they can after being tanned in the manner stated, be submitted to complementary operations which do not come within the scope of the present invention. I

What we claim as our invention and desire to secure by Letters Patent of the United States is:

l. The method of tanning hides connsting in treating them in stationary vats containing tannic solutions, without addition of any other acting agent-than tannin, at aconcentration of 7 to 35% of extract of tannin according to the quality and thickness of the skins to be treated, the shns being immersed in the cold tannic solution the temperature oi the bath together with the skins immersed therein being thereupon raised in a relatively short time to that of .the animal during its life and maintained 7 practically at said life temperature i without removing the skins until the comp etion oi the tanning. k 2. The method of tanning hides 1 in treatin them in stationary vats containing tannic so utions, without addition of any other acting agent than tannin, at a concern tration corresponding from 7 to 35% of extract of tannin according to the quality and thickness of the skins to be treated, the

skins being secured on. battens or frames and immersed in the cold solution of tannin, r

the temperature of the bath to ether with the immersed skins bein raised gradually or rogressively, in a relatively short time to t at of the animal, whose skin is treated, during its life, and maintainedat said his temperature for a period va 1: f

in from the vats, means being provided for relative the bath;

3. The method of tanning hides consisting' in treating them in stationary vats conmovement of the battens or frames and of taining tannlc solutions, without addition of any other acting agent than the tannin, at a concentrationcorresponding ham 3 to 35% of extract of tannin according to the temperature and without removing the skins .quality and thickness of the skins to be from the vats for a period varying from 1 treated, the tannic solution being constantly to 15 days, substantially as set forth. kept in movement and the skins being se- In witness whereof we have signed this cured on fixed battens orframes and also specification in the presence of two wit- 1lzeing immersed in the oiyldhtanm'c solution nesses. I v

ept in movement, an t e temperature GIACOMO B0510 raised gradually and quickl that is to say progressively and in a relat iely short time, v ANTONIO PERADOTTO' to the temperature of the live body heat Witneses:

of. the animal whose skin is being treated Noun Wmmsrons, and maintained praetically at said live body Tmcnnro Awe. 

